The present invention relates generally to motor control methods and particularly to automatic methods for shutting off motors under various operating conditions encountered in the operation of floor cleaning machines.
A floor cleaning machine for cleaning large floor areas as in hotels, offices and the like will typically include two motors. A first motor 60, sometimes referred to as a brush motor, is coupled to a rotating agitator 64 which contacts the surface to be treated or cleaned. A second motor 96, sometimes referred to as a vacuum motor, is coupled to an air moving device 94 for creating directional air flow so as to remove cleaning solutions and/or debris from the surface being cleaned and placing the picked up solution and/or debris into a recovery vessel such as a tank 90.
One type of floor cleaning machines for which the present invention has particular application is a floor scrubber 10. In floor scrubbers, the rotating agitator 64 can be in the form of a brush. However, due to the particular floor surface to be cleaned or the particular cleaning operation desired to be performed, the rotating agitator 64 often is in the form of a pad 164 held on a pad holder 166 by a retainer 168. To maximize pad life and for maximum cleaning ability, it is desirable to invert the pad 164 on the pad holder 166 on occasion. Floor scrubbers 10 include some provisions for moving the agitator 64 between a raised and lowered position. In the lowered position, the agitator 64 is in its working position and engages the floor surface. In the raised position, the rotating agitator 64 is in a transport position elevated from the floor surface at least for ease of transport between cleaning surfaces or between its storage location and the surface desired to be cleaned. Typically, such provisions are in the form of a lift lever 56 which is pivoted by the foot of the operator. The brush motor 60 is controlled by an electric switch on the console of the floor scrubber 10. When the operator desired to invert the pad 164, the operator would move the lift lever 56 to raise the rotating agitator 64 off the floor to obtain access to the retainer 168 of the pad 164. However, the operator often forgot to turn off the electric switch controlling the brush motor 60. As the pad 164 and retainer 168 are positioned on the underside of the floor scrubber 10, visibility may be limited or otherwise restricted. Thus, injury to the operator may occur if the operator attempts to remove the retainer 168 and pad 164 without realizing the agitator 64 is still rotating.
Thus, a need exists to automatically shut off the brush motor 60 when the rotating agitator 64 is raised off the floor surface at least for safety reasons.
Also, it is clearly desirable to prevent solution from passing from the recovery tank 90 into the air moving device 94. One prior attempt to solve this problem was to provide a float operated mechanical switch in the recovery tank 90. However, at least due to the exposure of such switches to moisture in the recovery tank, reliability issues have arisen. Additionally, problems also occur (especially when the recovery tank 90 is close to being full but not full enough to turn off the mechanical switch) of the cleaning solution sloshing through the outlet of the recovery tank and being drawn into the air moving device 94. Thus, a preferred method of solving this problem is to provide a mechanical float 170 which shuts off the outlet of the recovery tank 90 and thus blocks fluid communication between the recovery tank 90 and the air moving device 94. The problem is that when the recovery tank 90 is full and the mechanical float 170 blocks off the outlet of the recovery tank 90, the vacuum motor 96 continues to drive the air moving device 94 but the cleaning solution and/or debris are not removed from the floor surface as air flow is blocked. However, the operator may not realize this has occurred until cleaning solution being pushed in front of the squeegee provisions 144 is visible beyond the sides of scrubber 10 or behind scrubber 10. Although the sound or pitch of the air moving device 94 may change when the air flow is blocked, the operator may not notice this change due to lack of attention or other distractions and can especially be difficult to ascertain when floor scrubbers 10 are designed and manufactured to reduce or deaden noise generation.
Thus, a need exists to automatically shut off the vacuum motor 96 when the air flow through the air moving device 94 is blocked such as when the recovery vessel such as a recovery tank 90 is full of solution and/or debris.